1. Field of the Invention
This invention relates to an automatic tracking apparatus which maintains good tracking between a rotary head scanning on tape and a recorded track on the tape by automatically detecting the tracking error. A video tape recorder (VTR, hereafter) used in this invention has rotary heads which are affixed to a piezoelectric element which displaces the heads in a lateral direction with respect to the recorded tracks.
2. Description of the Prior Art
Recently, the rotary heads in VTR are required to trace on recorded tracks with high-fidelity even upon slow motion or still picture reproduction. For satisfying this requirement, some VTRs have been developed recently, in which no tracking shifters are used and the rotary heads continuously scan the recorded tracks correctly from the starting point to the ending point of the recorded tracks. The operation principle of such VTRs is that the rotary heads are held via a piezoelectric element which displaces the heads in to the lateral direction with respect to the recorded tracks, and the rotary heads are moved so as to keep on-track by moving the piezoelectric element i.e. a (positionable element). In this case, control signals used to represent the direction and the amount of the deviation of the rotary heads must be provided from the recorded tracks. Such control signals are obtained by vibrating the rotary heads by a reference frequency f.sub.c of a sinusoidal wave signal (this vibration is called wobbling) and by synchronously detecting the thus generated envelope detection output.
However, in the conventional automatic tracking VTR which detects the envelope as described above, the cross talk of the chrominance signal reproduced from the different azimuth track reduces the S/N of the tracking error information, so that the operation of the automatic tracking is interferred with.